Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.33	9.817%	$237.5671	$237.57	$237.55	$237.60
Purchase #2	$104.64	6.585%	$111.5305	$111.53	$111.55	$111.50
Purchase #3	$208.99	7.868%	$225.4333	$225.43	$225.45	$225.40
Purchase #4	$36.53	8.786%	$39.7395	$39.74	$39.75	$39.70
Purchase #5	$84.46	6.115%	$89.6247	$89.62	$89.60	$89.60
Purchase #6	$211.38	10.516%	$233.6087	$233.61	$233.60	$233.60
Purchase #7	$59.74	6.390%	$63.5574	$63.56	$63.55	$63.60
7 purchase totals =	$922.07		$1,001.0612	$1,001.06	$1,001.05	$1,001.00